The invention relates to a TDD method between a base station and at least one mobile station using a Logical Control Channel LCCH and at least one Traffic Channel TCH.
In the case of Time Division Multiple Access (TDMA) methods, a so-called duplex link, which requires two physical channels, can be set up between a base station and at least one mobile station. It is thus possible for a subcriber to speak and listen at the same time. Time division separation is used in such duplex links, also being referred to as Time Division Duplex (TDD methods). Such a method is generally known, for which purpose reference is made to the document "Mobil-funknetze und ihre protokolle" Mobile radio networks and their protocols!, Chair of Communications Networks, Prof. Dr.Ing. Bernhard Walke, RWTH Achen, Winter Semester 94/95. This could be used, for example, in cordless telephone systems and in mobile radio networks, etc.
Logical control channels (LCCHs) are in general used for transmitting control information for signalling and controlling the system, which is not passed to the subscribers. Typical tasks which can be carried out with the aid of control information are signalling and switching of Traffic Channels, mobility management or access control to radio channels.
Traffic Channels (TCHs) are logical channels via which wanted information is interchanged between subscribers who are maintaining the link. Speech and data are transmitted in digital form and by means of various coding methods.
TDMA systems exist which have only one Traffic Channel in addition to a Logical Control Channel. Thus, for example, an intracell handover is not possible in these systems. An intracell handover occurs when a change in the radio channel takes place within a cell, and thus while maintaining the same base stations. The reason that an intracell handover cannot be carried out in this case is that the Logical Control Channel is still required to transmit signalling information, so that no additional time slot is available for setting up a further Traffic Channel. In addition, it would, of course, not be possible in such a case to set up a second Traffic Channel which could be active at the same time as the already existing Traffic Channel.
The same problem also occurs both in the downlink and in the uplink in TDMA systems having a relatively large number of time slots, to be precise when all the other Traffic Channels in addition to the Logical Control Channel are busy, and a further time slot is nevertheless still required for setting up an additional Traffic Channel.